1. Field of the Invention
The invention in general relates to transducers, and particularly to an electro-hydroacoustic projector for underwater use.
2. Description of the Prior Art
For various underwater applications, a need exists for a relatively low frequency acoustic projector operable over a relatively wide bandwidth.
In one type of commonly used transducer, the electro-hydroacoustic transducer, high-pressure working fluid is operable to move a radiating element, such as a piston, in accordance with a signal to be transmitted. The high-pressure fluid flow is modulated by means of a valve such as a spool valve movable about a center position and whose movement is governed by an electrodynamic driver which receives an input electrical signal. Thus, an input electrical control signal governs the movement of a large piston radiator.
To accommodate the high-pressure fluid flow necessary to move the relatively large piston, such systems are built to extremely close mechanical tolerances. Any foreign objects which may enter the fluid circuit can cause disruption of proper operation and accordingly various filters must be used in such systems. The use of filters requires periodic replacement, and additionally they are not 100 percent effective against foreign bodies.
Further, the pressures generally utilized may be thousands of psi and the fluid circuit requires rather demanding sealing arrangements to maintain proper operation.
The present invention may be operated at relatively low fluid pressures and completely eliminates the requirement for a relatively large piston radiating member, thus allowing the construction of a much smaller transducer.